Magnetic properties of intermediate incommensurate phase in EtMeSb[Pd(dmit)] studied by SR

SRによるEtMeSb[Pd(dmit)]の中間非整合相の磁性研究

河村 聖子   ; Guerin, L.*; 渡邊 功雄*; 加藤 礼三*

Kawamura, Seiko; Guerin, L.*; Watanabe, Isao*; Kato, Reizo*

分子性有機導体EtMeSb[Pd(dmit)]は、スピン1/2の2次元三角格子系で、=70Kでスピン1重項形成を伴って電荷分離相への1次相転移を示す。最近、高分解能X線構造解析により、この系は=105K以下で三角格子の歪み度合いが変調する中間非整合相を発現し、さらに =66.5K以下で整合の電荷分離相を発現することが報告された。そこで我々は、非整合及び整合相における磁気ダイナミクスを調べるため、ミュオンスピン緩和(SR)測定を行った。その結果、以下でのミュオンスピン緩和率の顕著な増加に加えて、以下でわずかな緩和のエンハンスメントが観測された。我々の結果は、格子と強く結合した磁気相関がで変化することを示唆している可能性がある。

Molecule-based organic conductor EtMeSb[Pd(dmit)] is a two-dimensional triangular lattice system with spin-1/2. The system is suggested to undergo a first order transition to a charge separation (CS) phase with formation of a spin-singlet state at = 70 K. Recently, it was found by a high-resolution X-ray diffraction measurement that an intermediate incommensurate phase, where the degree of spatial distortion of the triangular lattice is modulated, appears below = 105 K and then the commensurate CS phase appears below = 66.5 K. We performed SR measurements on this system to investigate magnetic dynamics in the incommensurate and commensurate phases. A small enhancement of the muon spin relaxation was observed below , in addition to a drastic increase in the muon spin relaxation rate below . Our result may indicate that the magnetic correlation significantly coupled with the lattice structure changes at .